1. Field of the Invention
This invention relates to a light-emitting device, more particularly to a light-emitting device having high heat conductivity and high heat dissipation.
2. Description of the Related Art
A light-emitting device is a semiconductor component which may transform electrical energy into light energy, and has been utilized widely in the field of illumination because it has advantages of low power consumption, small volume, high transforming efficiency, long service life, and others. Specifically, a high power light-emitting diode having high luminance and high efficiency has been the focus of many researches.
However, the light-emitting device may produce a great amount of heat in the course of transforming electrical energy into light energy. If the heat accumulated in the light-emitting device is not effectively dissipated, the light-emitting device may deteriorate and the service life and the product stability of the light-emitting device may be reduced. Additionally, the heat produced from the high power light-emitting device designed for high luminance may be more significant. Therefore, in addition to enhancing the luminance of the highpower light-emitting device, the heat dissipation problem encountered in the high power light-emitting device is also required to be solved in the art.
In order to alleviate or even eliminate the heat problem produced in the light-emitting device, a heat conductive substrate is used to conduct and dissipate the heat produced from the light-emitting device. Alternatively, a mixture of an epoxy resin and metal powders (for example, silver powders) is used to package the light-emitting device. However, the heat resistance of the epoxy resin is inferior, and thus the epoxy resin is liable to deterioration or yellowing when being exposed to an elevated temperature environment. The light transmittance and the light output amount are decreased accordingly. Therefore, such a mixture is not suitable for the high power light-emitting device. Furthermore, although the heat conduction purpose may be achieved using the metal powders, the metal powders are opaque and may affect the light extraction efficiency of the light-emitting device. The aforesaid heat-dissipation methods may not be effectively used.